New bacterial enzyme discovered
doi:10.1038/nindia.2021.83 Published online 7 June 2021
Researchers from the Centre for Cellular and Molecular Biology (CCMB) in Hyderabad have discovered an enzyme that helps maintain the stability and integrity of cell walls in bacteria such as Escherichia coli1.
The enzyme, named LdtF, plays a vital role in the formation of covalent linkages between the bacterial outer membrane and an inner polymer layer that protects bacteria from environmental stress, the CCMB team has found.
This study, they say, will help understand the fundamental bacterial cell wall biology and identify alternate drug targets for the development of new antimicrobials.
The cell wall of gram-negative bacteria has an outer membrane and an inner membrane. Sandwiched between these two membranes is a layer of peptidoglycan, a polymer of amino acids and sugars that form a protective layer. A lipoprotein is known to link the outer membrane to the layer of peptidoglycan. However, it remains unknown how linkages between the lipoprotein and peptidoglycan are modified.
To better understand this, the scientists studied the cell wall biology of a well-studied strain of E. coli. Using genetic and biochemical approaches, the researchers, led by Manjula Reddy, identified that LdtF could cleave the lipoprotein from the peptidoglycan.
They found that the absence of LdtF enhanced growth defects and increased the peptidoglycan-lipoprotein linkages in the bacteria. The presence of this enzyme, however, decreased the levels of peptidoglycan-bound lipoprotein, suggesting its role in modulating the peptidoglycan-lipoprotein linkages.
Such LdtF-mediated modulation of the cell wall gives bacteria flexibility and a survival advantage in fluctuating environmental conditions, says Reddy.
1. Bahadur, R. et al. Cleavage of Braun’s lipoprotein Lpp from the bacterial peptidoglycan by a paralog of L,D transpeptidases, LdtF. Proc. Natl. Acad. Sci. Unit. States. Am. 118 (2021) Doi:10.1073/pnas.2101989118